At a Glance

The massive iceberg is the sixth largest to break off the glacier since 2001.The iceberg first appeared as a rift in the glacier in September.The iceberg measured 87 square miles before it began to fragment.

An iceberg five times the size of Manhattan has calved from West Antarctica's Pine Island Glacier.

The massive iceberg — the sixth largest to break off the glacier since 2001 — calved from the glacier on Wednesday and quickly as it pulled away into the Amundsen Sea, Stef Lhermitte,an assistant professor in the Department of Geoscience and Remote Sensing at Delft University of Technology in the Netherlands, tweeted on Wednesday.

The iceberg measured 87 square miles before it began to fragment. It first appeared as a rift in September and was the largest chunk of nearly 116 square miles of ice that separated from the glacier this week.

Lhermitte told weather.com that although there have been numerous large calving events in recent years, the size of recent icebergsmeans little.

"First calving events are part of the natural cycle of glacier tongues," Lhermitte said. "They grow (sometimes for a long period) and then calve. Similar to your fingernail. So to understand the significance of a calving event, we need to understand the long-term behavior. In that context, it is clear that since 2015, the calving front retreated when compared to records extending back to early 1970s."

Iceberg B-46 breaking off from Pine Island Glacier in West Antarctica.

(Landsat OLI imagery processed by Stef Lhermitte, Delft University of Technology)

Recent calving events and the retreat of the calving front highlights the impacts global warming is havingon polar ice shelves andrising seas.

In 2017, a,one of the largest in Antarctica.

Greenhousegas emissions-driven global warming is being blamed for an incredible amount of ice lost each year in Antartica.

Pine Island loses an estimated 45 billion tons of ice each year to the ocean, which amountsto 1 millimeter of global sea level rise every eight years.

In 2016, a study led by Seongsu Jeong and Ian Howat of Ohio State University found that Pine Island Glacier was “.”

The researchers noted thatthe ice shelf had developed a new way of losing ice, rifts were forming in the center of the huge glacier rather than along its edges, suggesting the warmer waters reaching the base of the glacier is undermining it.

“Rifts usually form at the margins of an ice shelf, where the ice is thin and subject to shearing that rips it apart,” said study leader, associate professor ofat Ohio State. “However, this latest event in the Pine Island Glacier was due to a rift that originated from the center of the ice shelf and propagated out to the margins. This implies that something weakened the center of the ice shelf, with the most likely explanation being a crevasse melted out at the bedrock level by a warming ocean.”

With each break, the glacier becomes more and more unstable, possibly leading to a runaway retreat in ice.

Howat noted in 2016 that it's "no longer a question of whether the West Antarctic Ice Sheet will melt, it’s a question of when."

"This kind of rifting behavior provides another mechanism for rapid retreat of these glaciers, adding to the probability that we may see significant collapse of West Antarctica in our lifetimes,” Howat said.

In atweet on Wednesday, Lhermitte noted that a new rift is already developing on the glacier, indicating a future calving event. The satellite image also shows how the latest iceberg is quickly fragmenting.